Crude protein is the total amount of protein in dry food, including both digestible and indigestible forms.
It is calculated based on the nitrogen content of the food since proteins are made up of amino acids, which contain nitrogen.
The term “crude” indicates that this measurement does not differentiate between different types of proteins or their sources.
Example:
- A dry cat food bag may list “crude protein: 30%.”
This percentage represents the total protein content in the food derived from various ingredients.
Importance of Protein for Cats #
Not all proteins are equal.
Animal-based proteins (e.g., chicken, fish, egg) are considered higher quality and more digestible for cats than plant-based proteins.[3]
Thus, dry cat foods should prioritize animal-based proteins as the primary ingredient.
A study found that some vegetarian cat foods did not meet AAFCO amino acid requirements, highlighting the importance of evaluating protein quality.[2]
Another study showed that high protein foods with similar phosphorus levels as lower protein foods increased levels of uremic toxins in cats with reduced kidney function.[1]
Insufficient Protein Intake:
- Muscle wasting and weakness
- Poor coat condition
- Compromised immune function
- Impaired growth in kittens
Excessive Protein Intake:
- High protein levels, especially from low-quality sources, can strain cats’ kidneys and liver, potentially causing organ damage over time.
Example:
- A food with 35-40% crude protein is beneficial for a growing kitten to support rapid growth and development.
Sources of Crude Protein #
The quality of crude protein depends on its source.
High-quality proteins typically come from animal sources, providing all the essential amino acids cats need.
In contrast, plant-based proteins may lack certain amino acids and are less digestible.
- Animal-based Proteins: Chicken, beef, fish, turkey, lamb.
- Plant-based Proteins: Soy, corn gluten meal, pea protein.
Example:
- A premium dry cat food might list chicken meal (a high-protein source) as the first ingredient, ensuring a higher crude protein quality.
Interpreting Crude Protein in Dry Cat Food #
Understanding the percentage of crude protein on a pet food label is crucial, but it’s equally important to consider the source and quality of that protein.
- High-Quality Proteins: Look for specific named meat meals or fresh meats.
- Lower-Quality Proteins: Be wary of generic terms like “meat by-products” or plant proteins listed high in the ingredient list.
Example:
- Food A: “Chicken meal, turkey meal, fish meal” – High-quality animal protein sources.
- Food B: “Corn gluten meal, soybean meal” – Lower-quality plant-based proteins.
Dry Matter Basis Comparison #
To accurately compare the protein content of different foods, it’s important to convert the “as fed” values to a dry matter basis, which excludes moisture content.
The formula for Calculating Dry Matter
The dry matter amount (A) in percentage is calculated using the following formula:
Dry matter % = (“As fed” nutrient % / (100% – Moisture %)) x 100%
For example, if a dry food contains 32% protein and 10% moisture on an “as fed” basis, the dry matter protein would be:
Dry matter protein % = (32% / (100% – 10%)) x 100% = 35.6%
How much Protein? #
The Association of American Feed Control Officials (AAFCO) and other organizations provide guidelines on protein content in dry cat food:
Kittens
- AAFCO: Minimum 30% crude protein[3]
- FEDIAF: Minimum 30% crude protein
- PFIAA: Minimum 30% crude protein
Premium kitten foods may contain up to 40% protein to support rapid growth.[3]
Adult Cats
- AAFCO (USA): Minimum 26% crude protein on a dry matter basis[3]
- FEDIAF (Europe): Minimum 25% crude protein
- PFIAA (Australia): Minimum 25% crude protein
However, many experts recommend higher levels, around 30-35%, from animal-based sources for optimal health.[3]
Senior Cats
While there is no separate AAFCO profile for senior cats, some research suggests moderately higher protein levels (around 30-35%) from high-quality sources may help preserve lean body mass as cats age. However, cats with kidney disease may require lower protein levels prescribed by a veterinarian.
Bottom Line #
- Read Labels Carefully: Look beyond the crude protein percentage and examine the sources.
- Prefer Animal Proteins: Choose foods with high-quality animal-based proteins listed first.
- Consult a Vet: Regular dietary reviews with a veterinarian can help meet your cat’s protein needs.
Common Questions about Protein #
Can cats eat too much protein?
Excessive protein from low-quality sources can strain the kidneys and liver. However, cats generally tolerate high-quality animal-based proteins. Consult with a veterinarian for specific dietary needs.
Are plant-based proteins suitable for cats?
Plant-based proteins are less digestible and bioavailable for cats compared to animal-based proteins. While they can be included, animal-based proteins should be the primary source.
How can I determine the protein quality in dry cat food?
Look for animal-based proteins listed as the first or second ingredient. Reputable brands often provide information on protein source, digestibility and amino acid profiles.
Can kittens and adult cats eat the same dry cat food?
It’s generally recommended that kittens be fed a diet specifically formulated for their higher protein and energy needs. Adult cat food may not provide adequate nutrition for proper growth and development.
Can dry cat food with high protein levels cause kidney problems?
High-quality animal-based proteins are usually well-tolerated by cats with healthy kidneys. However, cats with existing kidney disease may need a lower-protein diet prescribed by a veterinarian.
Sources:
[1] https://pubmed.ncbi.nlm.nih.gov/7996232
[2] https://pubmed.ncbi.nlm.nih.gov/37097066/
[3] https://pubmed.ncbi.nlm.nih.gov/26225610/
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6968870/
[5] https://www.semanticscholar.org/paper/f7653bbf1b84ad0afbcc1586fb98ca590270826c
and also:
https://fediaf.com/self-regulation/nutrition.html
https://pfiaa.com.au/resources/
https://www.vin.com/apputil/content/defaultadv1.aspx?id=7124888
